Ask for a math problem about function F (x) = ax ^ 2 + (b-2) x + 3 is the even function defined on [2a-1,2-a]. Find the range of function

Ask for a math problem about function F (x) = ax ^ 2 + (b-2) x + 3 is the even function defined on [2a-1,2-a]. Find the range of function

2a-1=a-2
a=-1
f(x)=-x²+(b-2)x+3
f(-x)=-x²-(b-2)x+3
f(x)=f(-x)
b=2
Then f (x) = - X & # 178; + 3 - 3 ≤ x ≤ 3
-6≦f(x)≦3